Characterization of (2R,4S)- and (2R,4R)-2-Methylfentanyl and their differentiation from cis- and trans-3-Methylfentanyl

In the United States, the illicit drug market has recently been flooded with fentanyl and fentanyl-related compounds. The ability to easily synthesize fentanyl-related compounds by simply using different precursors has added to the difficulty of forensic analyses. Often, developed methodologies and/or certified reference materials necessary for analyses are not available to forensic laboratories. Recently, a sample of 3-methylfentanyl was tentatively identified at a forensic laboratory. It is possible to have other alkyl sub-stitutions on the piperidine ring in fentanyl; therefore, it was necessary to synthesize 2-methylfentanyl to confirm the alkyl position in the submitted sample. 2R,4R-2-Methylfentanyl and 2R,4S-2-methylfentanyl were synthesized and analyzed via nuclear magnetic resonance spectroscopy, gas chromatography/mass spectrometry, and Fourier transform infrared spectroscopy. The comparison of the two compounds confirmed the isomers of 2-methylfentanyl can be distinguished from the isomers of 3-methylfentanyl with analytical methodologies typically found in forensic laboratories. Published by Elsevier B.V.